The present invention relates to a method and an apparatus for maintaining or restoring freshness of vegetable bodies such as plants, vegetables, fruits, flowers, flowering plants and leaves. Furthermore, the present invention relates to a method and an apparatus for planning to maintain or restore freshness of vegetables and fruits.
Methods of preserving freshness of vegetables and fruits have heretofore been practised such as a method, wherein the vegetables and fruits are immersed into or sprayed with cold water or cold brine. Due to the lowered temperature of the vegetables and fruits, living functions thereof are controlled namely, consumption of activated physiological energy is avoided by a reduced respiration value, evaporation is controlled and deteriorated product quality due to withering and the like is prevented other methods. Numerous variations of this technique have been proposed.
Several examples of these proposals are listed here, and differences thereof from the present invention will hereunder be described.
Japanese Patent Laid-Open (Kokai) No. 35165/72 discloses a method wherein the vegetables and fruits are immersed in or sprayed with an aqueous solution containing 0.2-1.0% of sodium acetate, said aqueous solution being added thereto with low concentration brine,
Japanese Patent Laid-Open (Kokai) No. 159783/80 discloses a method wherein the vegetables and fruits are vacuum-treated, subsequently, sprayed with cold water, and thereafter, stored under reduced pressure.
Japanese Patent Laid-Open (Kokai) No. 131345/80 discloses a method wherein the vegetables and fruits are immersed in hypochlorous acid solution, rinsed with water, thereafter, immersed in anti-oxidant bactericidal water, and then, dehydrated and stored,
Japanese Laid-Open (Kokai) No. 159783/80 discloses a method wherein the vegetables and fruits are put into a vacuum tank, a cold water layer is formed on the surface of the vacuum tank by spraying to generate micromist in the vacuum tank, thereafter, the vacuum tank is drawn vacuum, cooled and stored, and
Japanese Patent Laid-Open (Kokai) No. 113227/81 discloses a method wherein the vegetables and fruits are passed through cold water showering, and placed in a refrigerator under low temperature and high humidity, to thereby hold freshness thereof.
All of the above-described proposals require considerably complicated apparatus which can lead to troublesome operations.
The following proposals disclose methods wherein, when stored, the vegetables and fruits are brought into contact with various additives for holding freshness.
Japanese Patent Laid-Open (Kokai) No. 60940/83 discloses a method wherein the vegetables and fruits are brought into contact with zeolite, silicic acid clay and the like,
Japanese Patent Laid-Open (Kokai) No. 143576/84 discloses a method wherein the vegetables and fruits are coated or sprayed with a member selected from the group consisting of L-ascorbic acid, ferrous sulfate, ferrous chloride and ferrous nitrate,
Japanese Patent Laid-Open (Kokai) No. 24152/85 discloses a method wherein the vegetables and fruits are immersed in or sprayed with an aqueous solution containing 1 weight part of lecithin taken to 10-5,000 weight parts of water, said lecithin being mixed with and dispersed in the water, and
Japanese Patent Laid-Open (Kokai) No. 49740/85 discloses a method wherein cold water is added thereto with 1-2 weight % of a member selected from the group consisting of propylene, glycol-glycerine-ethanol and salt as an antifreeze and 2-5 weight % of zeolite as a dehydrating agent.
It cannot be said that there are no problems about the additives themselves, and much consideration may be still required for holding freshness of the food products.
As methods wherein the vegetables and fruits are placed in a sealed vessel containing therein any one of various gases so as to hold the freshness thereof, there are methods as follows.
Japanese Patent Laid-Open (Kokai) No. 153753/85 discloses a method wherein the vegetables and fruits are placed in a gaseous atmosphere of any one of saturated hydrocarbons such as propane and butane or any one of halogenated hydrocarbons such as trichlorofluoromethane and trichlorotrifluoroethane, and
Japanese Patent Laid-Open (Kokai) No. 75756/74 discloses a method wherein the vegetables and fruits are stored in a sealed vessel in which gaseous values of nitrogen and oxygen differ from each other in accordance with the types of the vegetables and fruits.
These methods have various problems including the sealed vessel itself, the relationship between the sealed vessel and the gas generator, and the like.
In the case where cold water is used or brine is added to cold water in the above-described prior art, due to absorption of moisture and the like to some extent, evaporation of moisture from the vegetables and fruits can be controlled. However, remarkably improved freshness cannot be obtained. Furthermore, as for the cold brine, regulation of brine concentration (within several percent order) is needed in accordance with the types of the vegetables and fruits and the usage of salt amounts to a high value, so that this method cannot be recognized to be an easy and economical method.
As described above, according to the prior art, the apparatus and vessels require high costs and problems are involved in blending of additives and the relationship between the additives and food products, and further operating procedures are complicated as well.
In view of the above-described problems, the present invention has been achieved as the results of various studies to develop a method and an apparatus which affords greater economy by using a simple apparatus that is easy to operate. SUMMARY OF THE INVENTION
More specifically, the present invention contemplates in a method of maintaining or restoring freshness of a vegetable body, wherein at least part of the vegetable body is immersed in cold, low temperature water having supersaturated with dissolved air. Furthermore, the present invention contemplates an apparatus for maintaining or restoring freshness of a vegetable body, having a tank for immersing the vegetable body, wherein the tank for immersing the vegetable body comprises: a pressurized air chamber having an opening to be connected to a pressurized air supply source; and a chamber for immersing the vegetable body, communicable with said pressurized air chamber through pores of a porous separator wall member.
According to the present invention, the terms vegetable or vegetable body body refers to a part or the whole of individual vegetables such as branches, flowers and flowering plants, as well as greens and fruits.
According to the present invention, in order to maintain or restore freshness of a vegetable body, at least part of the vegetable body is immersed into cold, low temperature water supersaturated with air. In this case, with a vegetable body having a root system, it is preferable to immerse at least the root system. Furthermore, with a vegetable body having a cut, it is preferable to immerse at least the cut.
To dissolve air into water, pressurized air is used. According to the present invention, to effect satisfactory contact between the pressurized air and the water, the pressurized air is brought into contact with the cold, low temperature water through a porous separator wall member formed with pores.
According to the present invention, to dissolve air supersaturation levels for a short period of time, pores having diameters of 0.1-10 microns are used. However, the pores having diameters of about 1 micron, and particularly, comparatively uniform diameters of mean value of 1 micron are preferable because air can be dissolved supersaturation levels for a very short period of time. As a consequence, according to the present invention, any material can be used as the porous separator wall member only if the material is one having a multiplicity of pores, being water-resistant and corrosion-resistant, and having a mechanical strength capable of bearing the pressure of the pressurized air. As the materials satisfying these requirements, there are porous materials such for example as fine mesh porous glass and porous ceramics. Particularly, a material called silas porous glass, i.e. S.P.G. is preferable because the material is highly water-resistant and corrosion-resistant and easily obtainable.
In the apparatus according to the present invention, the tank for immersing the vegetable body includes at least a pressurized air chamber and a chamber for immersing a vegetable or vegetable body. The pressurized air chamber and the chamber for immersing the vegetable or vegetable body communicate with each other through the pores of the porous separator wall member having the pores so that the pressurized air can be dissolved in the water in the chamber for immersing the vegetable or vegetable body. In this case, the porous separator wall member may be formed to provide various shapes such as a plate shape, a box shape or a hollow cylindrical shape.
When the pressurized air chamber is formed to provide a cylindrical shape by use of the porous separator wall member, it is preferable to provide it in the chamber for immersing the vegetable or vegetable body because a contact area between the air and the water becomes large. When part of the chamber for immersing the vegetable body is formed to provide a cylindrical shape by use of the porous separator wall member, it is preferable to provide it in the pressurized air chamber. In any case, to uniformly raise the concentration of dissolving of the supersaturated air in the water, it is preferable to cause the water in the chamber for immersing the vegetable body to circulate suitably.
According to the present invention, the vegetable or vegetable body is immersed into the cold, low temperature water with supersaturated air. Thus more moisture and air are absorbed by the vegetable or vegetable body, so that, in the immersed vegetable body, biochemical reactions are facilitated, a high value of activated energy is accumulated and the water absorbing capacity of the vegetable body is enhanced. As a consequence, according to the present invention, even with a vegetable body that is deteriorated in quality due to withering and the like, the water absorbing capacity is restored as described above, so that the freshness of the vegetable body can be restored to a considerable extent.
In the apparatus according to the present invention, the pressurized air chamber and the chamber for immersing the vegetable or vegetable body communicate with each other through the pores of the porous separator wall member, whereby dissolving of the air into the cold, low temperature water in the chamber for immersing the vegetable body is enhanced. Thus the absorbing capacity of the vegetable body can be restored for a very short period of time. As a consequence, according to the present invention, maintaining and restoring the freshness of the vegetable body can be effected for a very short period of time.